1. Field of the Invention
The invention relates to a high-pressure fuel reservoir for a common-rail fuel injection system of an internal combustion engine, having a tubular base body, which has a substantially circular-cylindrical interior disposed centrally with respect to the longitudinal axis of the tubular base body, which interior communicates with a plurality of connection openings.
2. Description of the Prior Art
In common rail-injection systems, a high-pressure pump, optionally with the aid of a feed pump, pumps the fuel to be injected out of a tank into the central high-pressure fuel reservoir, which is known as a common rail. From the rail, fuel lines lead to the individual injectors, which are assigned one to each of the engine cylinders. The injectors are triggered individually by the engine electronics as a function of the engine operating parameters, in order to inject fuel into the combustion chambers of the engine. By means of the high-pressure fuel reservoir, the pressure generation and the injection are decoupled from one another.
One conventional high-pressure fuel reservoir is described in German Patent Disclosure DE 195 48 611, to name one example. The known high-pressure fuel reservoir withstands pressures of up to about 1100 bar.
The primary object of the invention is to enhance the high-pressure strength of the known high-pressure fuel reservoir by simple provisions.
In a high-pressure fuel reservoir for a common-rail fuel injection system of an internal combustion engine, having a tubular base body, which has a substantially circular-cylindrical interior disposed centrally with respect to the longitudinal axis of the tubular base body, which interior communicates with a plurality of connection openings, this object is attained in that the cross section of the tubular base body, in the portions in which the connection openings are disposed, is embodied in weakened form. Within the context of the present invention, it has been found that in the region of the intersections between the connection openings and the tubular base body, under internal pressure, critical tensile stresses occur. By the intentional weakening of the tubular base body, the high-pressure strength of the high-pressure fuel reservoir of the invention is enhanced.
A particular embodiment of the invention is characterized in that the connection openings discharge substantially tangentially into the interior of the base body, and that one weakening of the tubular base body is provided in the region of each of the connection openings. In operation of the high-pressure fuel reservoir of the invention, the interior of the tubular base body expands under the high pressure prevailing there. As a result of the intentional weakening of the tubular base body, the circular cross section of the interior in the unloaded state is deformed into an ellipse, which is also called ovalizing of the diameter. A primary apex of the ellipse is located in the region of the respective connection opening. As a result, in the region of the intersection between the tubular base body and the connection opening, a compressive stress in the circumferential direction of the tubular base body is induced. This compressive stress compensates for part of the critical tensile stress. As a result, the stress in the regions of the intersections that are at high risk is reduced.
A further embodiment of the invention is characterized in that one further weakening of the tubular base body is provided opposite, as viewed in cross section, each of the connection openings. As a result, the above-described effect of ovalizing the interior of the tubular base body is still further reinforced. This leads to a further enhancement in the high-pressure strength-of-the-high-pressure fuel reservoir of the invention.
A further particular feature of the invention is characterized in that the connection openings discharge substantially radially into the interior of the base body, and that one further weakening of the tubular base body is provided opposite, as viewed in cross section, each of the connection openings. As a result, the above-described effect of ovalizing the interior of the tubular base body is attained even in the case of a radially disposed connection opening.
Still another particular feature of the invention is characterized in that the weakening of the tubular base body is formed by a lip angle, an undercut, or a key face. These types of cross-sectional weakening have the advantage that they can be produced in a simple way. As a result, even in conventional high-pressure fuel reservoirs, the high stresses in the intersection region that occur under internal pressure can be reduced.